With the lack of any modern CPU upgrade path for the LGA 775 socket motherboards it's going to have to be a full platform upgrade to bring your old rig into the modern PC era. Of course, there is always eBay, with its lure of cheaper, second-hand components, but you're still going to be spending nearly £100 on an improved LGA 775 Core 2 Quad.

Even if you ignore the possibility of failing silicon in older, maybe worn-out CPUs, there's also the fact you're not getting a whole lot extra performance out of that older architecture anyways. A 3GHz+ Core 2 Quad is still not going to get the most out of either a HD 6950 or GTX 570.

So we opted to bring the Intel system bang up to date with a Sandy Bridge refit; pairing the superlative Core i5 2500K CPU with Asus's simple, but oh-so-effective P8P67 Pro. At just over £300 for the pair, and the unfortunate necessity of 4GB of DDR3 RAM; it's a pricey upgrade.

In terms of raw processing power, though, the i5 is twice as powerful as the ageing Q6600. It is only a quad-core design, with no HyperThreading, but the new architecture does run ring-buses around the older Kentsfield layout.

Despite the power of the 2500K, that 8800GTS is keeping it bottlenecked in gaming terms. Just as with the AMD rig then we have hit an impasse. You can't just upgrade one side of the PC, even if that side does incorporate a full platform upgrade, and expect to be hitting the frames per second we all deserve.

Benchmarks

DX10 gaming: Just Cause 2

Graphics upgrade

Like the AMD machine, in terms of a straight gaming frame rate upgrade, dropping in a brand new graphics card will instantly net you a fairly significant boost in performance. It's clear that on both the Intel and AMD side of things the 8800GTS is simply not powerful enough.

And again with the base machine staying unchanged apart from the graphics refit, it's the lowly, £82 XFX HD 5770 really takes the lead in instant gratification terms.

World in Conflict gives the most serious change with framerates going up by nigh-on 200%. That Core 2 Quad Q6600 was being massively bottlenecked by the 8800GTS.

But there the good news ends for this old system, and especially that classic ol' quad-core CPU. The processor simply doesn't have enough left in the tank to provide enough performance to keep any speedier GPUs fed properly. Only in the rather GPU-centric DiRT 2 does the framerate really go up any further, with the other three GPUs held back by the Intel processor.

The Nvidia cards here demonstrate just what a good pairing they make with the Intel platform. The GTX 460 especially looks like a bargain, performing almost as well as the HD 6950 in Just Cause 2 and DiRT 2. If you wanted a stop gap card, the GTX 460 would make the platform upgrade a little cheaper, and ready for a second in SLI.

Benchmarks

DX10 gaming: World in Conflict

The Intel upgrade

As the performance leader in processor terms Intel hasn't needed to provide as much of a consistent upgrade path as its rival AMD. After all, when your new architecture is so much better than the previous generation, as with the LGA 775 and LGA 1156/1155, the argument for a full platform upgrade holds more weight.

But it does make things more expensive for the loyal Intel upgrader, generally doubling, at least, the price of a similar upgrade on an AMD platform. As we've explained there's really nowhere for you to go in terms of CPU upgrade on the LGA 775 socket, and that Q6600 isn't going to hold any sway if you want to drop in either a HD 6950 or GTX 570 for some serious gaming grunt.

Whither Lynnfield?

So where next? You might think that avoiding the latest generation of Sandy Bridge chips for the LGA 1156 Lynnfield processors might give you similar performance for a fraction of the upgrade cost, but you're still going to be looking at a whole new motherboard and CPU combo.

The only place you're saving money down that route is on the motherboard. P55 boards are reasonably inexpensive now, around the £100 mark, but the gamer's CPU of last year, the Core i5 760 is the same price as the far superior Sandy Bridge stunner. OK, you may be saving an extra £20 on a board but that's not a huge saving and the performance upgrade is significant.

So with the money spent and the Sandy Bridge platform all set up and raring to game, what do we do about graphics cards?

Well, now we've gotten that GPU-hobbling Q6600 out of the way we can now look at the Nvidia side of the graphics divide. When you put the top AMD CPU in the test up against the 2500K across the four GPU upgrades, it's immediately evident how weak the Nvidia cards are on the AMD side compared with the full potential unlocked by the Intel CPU. Even the GTX 460 performs far better on the i5.

There is now clear water between the HD 6950 and the more expensive GTX 570. The raw power of the 2500K means that there is absolutely no CPU bottleneck anywhere along the line, meaning that for every penny spent on a graphics card you know you are getting the absolute maximum performance you can out of it.

That said, as a full upgrade package, the platform purchase combined with a GTX 570 would make for around £600 of upgrade cash. Providing you've already got a decent PSU, chassis and are already running Win7 64, then that's not a bad price for essentially a brand new, super-fast, gaming PC.

If you're looking for a cheap option this isn't it. We'd generally say that £500 is a good limit to put on the cost of an upgrade before you start looking around at pre-built rigs. With that in mind purchasing a HD 6950 instead of the Nvidia card is a sensible way to go. They're almost £100 cheaper than the GTX 570, and can come with some serious untapped potential in terms of both overclocking and BIOS flashing.

The Intel side of the upgrade world is definitely the expensive side then, but it does have the edge in serious performance terms, if not quite in affordability.